2. Crystalline Structures
Single CrystalsSingle Crystals Polymer SpherulitesPolymer Spherulites
Sharmistha Datta & David J. W. Grant,Sharmistha Datta & David J. W. Grant, Nature Reviews Drug DiscoveryNature Reviews Drug Discovery 3,3,
42-57 (January 2004)42-57 (January 2004)
11. Kristal tunggal
2θ
Pada 20.6 °2θ, Hk Bragg
terpenuhi pada bidang
(100) & menghasilkan
sebuah puncak difraksi.
Bidang (110) seharusnya
menghasilkan difraksi pada 29.3
°2θ; tetapi tidak ‘properly aligned’.
Hanya acah latar yang terlihat.
Bidang (200) paralel dengan bidang
(100), sehingga menghasilkan
difraksi.
16. Tg & Tm
Differential thermal analyzerDifferential thermal analyzer
(DMA)(DMA)
Ref. such as AluminaRef. such as Alumina
At const. rate of T increaseAt const. rate of T increase
Endotherm: TmEndotherm: Tm
Small amount of sample, fastSmall amount of sample, fast
data and accuracydata and accuracy
Disadv: weak signal forDisadv: weak signal for
crystallinecrystalline
Heat change – DifferentialHeat change – Differential
scanning calorimetry (DSC)scanning calorimetry (DSC)
Keep temperature of sampleKeep temperature of sample
the same as that of Referencethe same as that of Reference
Monitor the current flowMonitor the current flow
17. Crystallinity by DSC
Example:Example:
Crystallinity ofCrystallinity of
PolyethylenePolyethylene
%100% ×
∆
∆
= °
f
obs
f
H
H
ityCrystallin
Q: “Where is my polymer in
this table?”
Table: Heats of fusion of 100%
crystalline polymers
18. Dilatometry
DilationDilation or change inor change in
specific volumespecific volume Computing crystallinityComputing crystallinity
Liquid of
known density
and thermal
expansion
coefficient
Polymer
∆V
ecrystallintotallyamorphous
ecrystallinpartiallyamorphous
vv
vv
C
−
−
=%
19. Dilatometry
Example: NylonExample: Nylon
How would you findHow would you find
the density (i.e.the density (i.e.
specific volume) ofspecific volume) of
this crystal given thethis crystal given the
size and shape?size and shape?
ecrystallintotallyamorphous
ecrystallinpartiallyamorphous
vv
vv
C
−
−
=%
Youyong Li and, William A. Goddard III
Macromolecules 2002 35 (22), 8440-8455
20. Wide angle x-ray
scattering/diffraction
X-rays: light withX-rays: light with
wavelength ~0.1-wavelength ~0.1-
10Å – the same10Å – the same
length scale aslength scale as
interatomicinteratomic
distancesdistances
Diffraction occursDiffraction occurs
only at specificonly at specific
angles, given by theangles, given by the
Bragg eqn.Bragg eqn.
θλ sin2dn =
23. What if it’s not a single crystal?
PolycrystallinePolycrystalline
samples looksamples look
different.different.
Example: HighlyExample: Highly
crystalline polymercrystalline polymer
with (mostly)with (mostly)
oriented crystallites.oriented crystallites.
Diffraction spots areDiffraction spots are
blurred into lines.blurred into lines.
24. What if it’s not a single crystal?
PolycrystallinePolycrystalline
samples looksamples look
different.different.
Example: HighlyExample: Highly
crystalline polymercrystalline polymer
with no orientationwith no orientation
of crystallites.of crystallites.
Diffraction spots areDiffraction spots are
blurred into fullblurred into full
circles.circles.
25. What if it’s not crystalline?
Diffraction circlesDiffraction circles
become much lessbecome much less
defined and blurred.defined and blurred.
Sharpness of circlesSharpness of circles
gives a clue togives a clue to
crystallinity.crystallinity.
26. Polymers
(see Roe: Methods of X-ray and Neutron Scattering in Polymer Science (2000))
semicrystalline poly(3-hydroxybuyrate)
27. Polymers
(see Roe: Methods of X-ray and Neutron Scattering in Polymer Science (2000))
semicrystalline poly(3-hydroxybuyrate)
note amorphous scattering region
28. Polymers
(see Roe: Methods of X-ray and Neutron Scattering in Polymer Science (2000))
Degree of crystallinity
Pattern consists of relatively sharp crystalline peaks +
amorphous scattering
Comparing intensities of the two ––> % crystallinity
29. Polymers
(see Roe: Methods of X-ray and Neutron Scattering in Polymer Science (2000))
Degree of crystallinity
Pattern consists of relatively sharp crystalline peaks +
amorphous scattering
Comparing intensities of the two ––> % crystallinity
Problems:
small crystallite size broadens peaks
extensive amounts of crystal imperfections
thermal motion
30. Polymers
(see Roe: Methods of X-ray and Neutron Scattering in Polymer Science (2000))
Degree of crystallinity
Pattern consists of relatively sharp crystalline peaks +
amorphous scattering
Comparing intensities of the two ––> % crystallinity
Methods for separation:
guess
measure 100% amorphous specimen
31. Polymers
(see Roe: Methods of X-ray and Neutron Scattering in Polymer Science (2000))
semicrystalline polydimethylpropiolactone
How was this photo taken?
Why does it look like this?
32. An estimate of crystallinity
The crystallinity can beThe crystallinity can be
estimated by comparingestimated by comparing
the areas of the peaksthe areas of the peaks
due to the amorphousdue to the amorphous
polymer with those ofpolymer with those of
the crystalline phase:the crystalline phase:
%C=A%C=Acrcr / (A/ (Acrcr + A+ Aamam))
K.A. Moly et al. / European Polymer Journal 41
(2005) 1410–1419;
34. Other methods: IR & NMR
Ying Zheng,, Merlin L. Bruening, and,
Gregory L. Baker
Macromolecules 2007 40 (23), 8212-
8219
35. Conclusion: A comparison
Method of
Analysis
Advantages Disadvantages
Differential
Scanning
Calorimetry
Fast, easy; You’re probably
going to use DSC anyway for Tg,
etc.
Need literature values of
heat of fusion for 100%
crystalline polymer for
comparison; thermal
history an issue.
Dilatometry A simple way to measure
polymer crystallinity based on
changes in volume.
Pure crystalline specific
volume must be known.
X-ray scattering Can determine precise crystal
structure.
Difficult to analyze data,
determine structure.
Polarized Optical
Microscopy
A quick way to see if a polymer
is crystalline.
Other factors (like strain
in the polymer) can cause
birefringence; difficult to
quantify.
